At present, the profit of the telecommunication industry is reducing progressively, and the telecommunication operators are realizing the income increase by expanding the market share and the service type, and at the same time they also pay more and more attention to saving the operation cost (OPEX), and the energy consumptions of the equipment is an important part of the OPEX.
The universal mobile telecommunications system (UMTS) can be divided into several main components: one or more core networks (CN) which is responsible for establishing and controlling the user session and the UMTS terrestrial radio access network (UTRAN) which controls the air interface access. The UTRAN includes two network elements: a radio network controller (RNC) and a NodeB, wherein the NodeB further includes the baseband processing unit (BBU) and a radio frequency processing unit (RU). The architecture of the UTRAN is shown in FIG. 1. The main functions of the BBU include the baseband processing function finishing the Uu interface (channel coding, multiplexing, modulating and spread spectrum and so on, which are suitable for air transmission), the Iub interface function with the radio network controller (RNC), signaling processing, local and remote operation maintenance function, and the function for monitoring the working state of the NodeB system and reporting alarm information. The main function of the RU includes several following modules:
an intermediate frequency module: configured to finish the function of modulating-demodulating, upper and lower digital frequency conversion, A/D conversion of the optical transmission;
a transceiver module: configured to finish the conversion function from the intermediate frequency signal to the radio frequency signal;
a power amplifier: configured to finish the enhancement function of the signal;
a filtering module: configured to finish the filtering function of the signal.
It can be seen from FIG. 1 that one RNC generally includes a plurality of NodeBs, and one NodeB generally includes one baseband processing unit (BBU) and a plurality of radio frequency processing units (RU). Therefore, if the power consumption of the radio frequency processing unit is saved, the power consumption of the whole UTRAN will be saved greatly.
The high speed downlink packet access (HSDPA) is a kind of technology put forward in Release-5 of the 3rd generation partnership project (3GPP), which is used for improving the network data throughput in the downlink direction (from the network to the terminal), and the peak value of downlink speed of the cell and individual user that are designed by HSDPA can reach to 14.4 Mbps. Subsequently, in order to make the peak value of downlink speed higher, the new HSPA+ technologies are introduced. These technologies includes the DL 64QAM high-order modulation and multi-input multi-output (MIMO) antenna technology put forward in Release-7, and the multi-carrier (DC) HSDPA technology put forward in Release-8, and the DC HSDPA+MIMO technology put forward in Release-9.
The MIMO utilizes a plurality of antennas to inhibit the channel from declining, which can improve the wireless channel capacity and the spectral utilization rate in the case that the bandwidth is not added. After the MIMO is introduced, the peak value of the speed of the cell and individual user is 28.8 Mbps in the case of MIMO+16QAM, and it can reach to 43.2 Mbps in the case of MIMO+64 QAM. However, in order to support the MIMO technology, the transmitting end needs to modulate data to two irrelevant antennas and send the data at the same time, and the receiving party also needs to receive the data from two irrelevant antennas at the same time and performs demodulation. The technological principle diagram of the MIMO provided by the 3GPP TS 25.214 is shown in FIG. 2.
There are two pilot configuration modes of the MIMO on two antennas:
one antenna sends the P-CPICH channel in the modulation mode of Antenna1, and the other antenna transmits the P-CPICH channel in the modulation mode of Antenna2, that is, the master pilot—master pilot mode;
two antennas send the P-CPICH and the S-CPICH channels respectively in the modulation mode of Antenna1, that is, the master pilot—slave pilot mode.
It can be seen from FIG. 2 that the MIMO requires two sets of radio frequency processing units (RU), and each set processes the data on an antenna respectively. In the case of the same coverage, the MIMO cell in the master pilot—master pilot mode is configured, and the transmission power of the common channel configured by each corresponding RU is half of that of the non-MIMO cell, therefore, the total transmission power of the common channel of the two RUs is same with that of the non-MIMO cell; for the MIMO cell configured in the master pilot—slave pilot mode, the transmission power configured by the master pilot is same with that of the non-MIMO, and the transmission power of the slave pilot can be configured according to the actual condition, and the transmission power of other common channels in each RU are half of that of the non-MIMO cell, therefore the total transmission power of the common channel of two RUs has an additional power configured by the slave pilot than that of the non-MIMO cell.
Meanwhile, since the power consumption of RU is related to the transmission power and its power amplification efficiency. In the case of the same transmission power, the lower the power amplification efficiency is, the greater the power consumption is. The power amplification efficiency of the RU is related to its output power, and for the same RU, the higher the output power is, the higher the power amplification efficiency is. Therefore, in the MIMO cell in the master pilot—master pilot mode, the total transmission power is same with that of the non-MIMO cell, however, the RU transmission power of each MIMO cell is only half of that of the RU of the non-MIMO cell, thus its power amplification efficiency is not higher than that of the RU of the non-MIMO cell, which leads that its total power consumption is higher than that of the non-MIMO cell. And for the non-MIMO cell in the master pilot—slave pilot mode, its total transmission power is higher than that of the non-MIMO, therefore its total power consumption is obviously higher than that of the non-MIMO cell.
At present, in the UMTS system, the cell is either configured fixedly in the MIMO mode or configured fixedly in the non-MIMO mode. The advantage of the cell configured in the MIMO mode is to improve the throughput rate of the user data, however, whether the terminal user in the MIMO cell can adopt the MIMO dual stream mode for scheduling is related to the terminal ability, the data amount of the terminal user and the CQI of the terminal user. If the cell still adopts the MIMO mode to transmit in the case that the terminal user does not meet the MIMO dual stream mode, the RU power consumption is wasted. The RU power consumption of the cell configured in the non-MIMO mode is a bit smaller than that of the MIMO cell; however, the MIMO terminal user is unable to experience the high speed data throughput rate of the MIMO.